title: Multivariate statistical characterization of charged and uncharged domain walls in multiferroic hexagonal YMnO3 single crystal visualized by a spherical aberration-corrected STEM.
abstract: A state-of-the-art spherical aberration-corrected STEM was fully utilized to directly visualize the multiferroic domain structure in a hexagonal YMnO3 single crystal at atomic scale. With the aid of multivariate statistical analysis (MSA), we obtained unbiased and quantitative maps of ferroelectric domain structures with atomic resolution. Such a statistical image analysis of the transition region between opposite polarizations has confirmed atomically sharp transitions of ferroelectric polarization both in antiparallel (uncharged) and tail-to-tail 180° (charged) domain boundaries. Through the analysis, a correlated subatomic image shift of Mn-O layers with that of Y layers, exhibiting a double-arc shape of reversed curvatures, have been elucidated. The amount of image shift in Mn-O layers along the c-axis is statistically significant as small as 0.016 nm, roughly one-third of the evident image shift of 0.048 nm in Y layers. Interestingly, a careful analysis has shown that such a subatomic image shift in Mn-O layers vanishes at the tail-to-tail 180° domain boundaries. Furthermore, taking advantage of the annular bright field (ABF) imaging technique combined with MSA, the tilting of MnO5 bipyramids, the very core mechanism of multiferroicity of the material, is evaluated.
authors.affiliation: Institute of Engineering Innovation, School of Engineering, The University of Tokyo , 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Ryo
authors.initials: R
authors.lastname: Ishikawa
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tohei
authors.forename: Hideo
authors.initials: H
authors.lastname: Kimura
authors.forename: Qiwen
authors.initials: Q
authors.lastname: Yao
authors.forename: Hongyang
authors.initials: H
authors.lastname: Zhao
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Wang
authors.forename: Dapeng
authors.initials: D
authors.lastname: Chen
authors.forename: Zhenxiang
authors.initials: Z
authors.lastname: Cheng
authors.forename: Naoya
authors.initials: N
authors.lastname: Shibata
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ikuhara